I have recently found Bitcoin (via Max Keiser) and really believe this is the way to go! :-)

I have a crappy computer with an old grapics card and i'm thinking of building a dedicated GPU miner. How would you build a computer that is only to be used for mining bitcoins and nothing else? Is it as simple as getting a computer with one of the more expensive (consumer) graphic cards and jam in fast RAM and disk and off we go?

Essentially its that simple. To make it efficient, you want the best MHash/Watt and MHash/$, since the power draw on a mining setup essentially nulls the profits unless you're running a big Radeon card with high ratios.

From the time I've spent lurking on the forums, and the sources posted herein, I think the general way you want to go regardless of budget is:

-Maximum ATI gfx card, even multiples that aren't running in Crossfire. (For separate device id's for separate instances of GPU miners)..... For some reason, ATI cards are several multiples faster than nVidia for mining for the price. An $80 radeon 5570 gets slightly more khashes/s than my $200 gtx460...... I'm unsure of the effects of mining with 2 cheap Radeon's non crossfire versus 1 fancy Radeon by itself. It may be mostly additive.

-Cheap CPU, unless you also want it to mine at the same time, then maximize it within your budget. GFX takes MAJOR priority however. More cores are better than faster cores. An AMD X6 or a newfangled intel i7 are ideal for maximum cores, but get expensive. Again, go AMD if price is a concern, they're plenty fast and 20-30% cheaper. GPU miner programs have minimal CPU impact.

-Minimal RAM, 2-4GB, depending on OS. This is just to have a responsive overall system. Bitcoin while generating on 4 of my 4 cpu cores uses ~28 MB of RAM.

-Minimal hard-disk. Doesn't need to be super fast or even big. Has the OS and your miners.

-High Airflow Case. A necessity since you'll likely be overclocking whatever you use. If price isn't an issue, get an aftermarket CPU cooler or water cooler. Even if you don't mess with CPU OC's, GPU OC'ing is quick and easy and generates a lot of heat. Antec's 300/600/900/1200 cases are loved by everyone, are inexpensive, and are regarded as among the best air cooling towers you can get.

-As efficient a PSU as possible. Probably with some decent wattage headroom for upgrades down the line as the hashing difficulty factor increases.

-Minimal Motherboard, unless you really wanna do a CPU OC. Make sure it accepts PCIe 2.0 x16, two of those slots if you want to run multiple cards (crossfire ready, etc), and the variety/quantity of RAM you want.

Buying hardware and power for mining is not going to be profitable. Best way is to use a machine you already have and power you don't pay for.If I'm actually wrong and there is a way to turn a profit with purpose-bought hardware, I'd love to know about it.

According to https://en.bitcoin.it/wiki/Mining_Hardware_Comparison, the 5770 draws about 100W and generates 150 Mhash/s. According to http://www.alloscomp.com/bitcoin/calculator.php, this should generate a block every 5 days. 5 days is 120 hours, times 100W is 12 kWh. Around here it's $0.20 per kWh, so that's about $2.50 per block for electricity. A block of 50 bitcoins is worth about $15 now, less $2.50 is $12.50 profit. The $99 card will be paid off after 8 blocks, so that's about 40 days at current difficulty. After that it's pure profit.

Most people assume difficulty will continue to rise, but I think it will level off soon, because except for unusual deals like this one, GPU mining is close to becoming unprofitable.

Im running a miner on my laptop with an ATI 5650 mobile. Gets roughly 48Mhash. if the TDP on wikipedia of 19W is accurate then these mobile chips give pretty good Mhash/W. Would be good if they put them on PCIe boards for a desktop

While the mobile cards would be great for MHash/watt, it would probably not be very much so on Mhash/$, thanks to the price barrier of miniaturization.If looking at the long term, as long as difficulty rate doesn't change toooo quickly, it may be worth the investment.

As it stands now, you can get an asus g73 (i think) for like $1300, which has a mobile radeon 5870... Matter of fact I nearly got that laptop for going back to the spring semester at university, but built my current desktop instead for an equal price. (Which the desktop turned out to be multiples more powerful in other ways, just apparently not bitcoin mining. EX: COMSOL or Solidworks simulations... ugh.)

I'm kindof on the fence about whether the increased investment (Which isn't so bad when you take into account the fact that a laptop is its own entire system, not "just" one super expensive component.) would be worth the decreased power draw. It may in the long run, but I suppose mileage may vary.

While the mobile cards would be great for MHash/watt, it would probably not be very much so on Mhash/$, thanks to the price barrier of miniaturization.

It would be great to have "mobile" GPUs in standard PCIe cards. I would definitely pay extra to get that improved performance per watt. I have already been using Mini-ITX/DTX machines for years, with "mobile" CPUs and chipsets in "desktop" systems.

One problem with using laptops for full-time number crunching is that the size necessitates small and noisy fans. Having those "mobile" components in an ATX case is pretty nice, since you can then have huge heatsinks and a large, slow fan. The only thing missing is a strong "mobile" GPU.

MoboGet one with 4x 16xPICe rails. All those 16xPCIe rails must have another rail in between EDIT: or a space at least. CPUs don't compare with GPUs for mining. If it says it can do 4-way CrossFire or SLI you are good to go. :-)

Graphics CardThere is only one option really, the ATI Radeon HD 5970, it gets you around 550 MHashes/sec.(Sorry, can't tell for sure. I got a 5870 and I get around 300MHashes/sec) They cost like 600 dollars each and you could be doing 600 MHashes/sec easily By OCing the GPU and UCing the memory. Which means it will cost you around 1 USD per MHash/sec + electric bill of it running. Also if you plan to get more than 2 in the 4-way mobo then the liquid cooling upgrade is mandatory.

You would have _the_ 20 TFLOPs computer though. This should be a 15 hundred 3K build depending on your choices.(Also with cooling it should get to at least 25 TFLOPS) which would mean you are paying 1 USD per 10 GFLOPS. Buy 40 of this and you get yourself a 1 PFLOPS cluster which would be max about 120K. If you do so you would account for half the current processing power in the Bitcoin network today or so. If you ask me this is a powerful build. I estimate the hashrate of 40 of this at around 100 GHashes/sec. That is enough to generate on average every 11 minutes.

What about someone who doesn't want to spend a lot of money on building a super mining computer but still wants to be able to generate a few bitcoins now and again through pooled mining? All I have right now is my Lenovo Thinkpad which generates ~ 1800 khash/s when running the bitcoin program and only ~800 khash/s when running a miner connected to Slush's server. Running the miner for two days straight generate me about 30 mBTC, which is far from exciting. My thought was to find some old towers, install Ubuntu on them, download the miner and then connect them to the mining pool. If I could get a couple free towers then I'd just use their CPUs and hopefully several of them would bring my total hash rate up to a point where I could get rewarded more.

Are there any options you guys know of other then forking out a bunch of cash for expensive graphics cards?

According to Ryo's paper, your old towers will not be profitable if you pay for electricity.

I don't pay for electricity. I'm just wondering if I should invest in getting a graphics card or whether that will pay off in the long run. I've been offered several free towers by some friends already, but the problem is connecting them to the internet. At the place I rent all we have is Wii-Fii so I would need wii-fii cards for each tower. The other option would be to set them up at school (where I also don't have to pay for electricity) but I'm not sure of the legal implications of that yet. It might be regarded as a "money-making" venture and therefore not allowed on school property.

From what I've read on this forum one decent graphics card is worth many, many CPUs as far as processing power goes.

I think that too but we should not discourage people for mining. The more miners there are, the stronger is the network.

You guys are doubtless correct, and I plan on purchasing bitcoins at some point soon, but there is an addictive adventure side to the mining process. It's like the gold fever of the California gold rush.